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MOD > Approach to skin nodules + nodular dermatitis > Flashcards

Approach to skin nodules + nodular dermatitis Flashcards

1
Q

What is a nodule?

A

*Circumscribed solid elevation greater than 1cm in diameter that usually extends into deeper layers of the skin

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2
Q

What causes formation of nodules?

A

Usually infiltration of
-inflammatory cells
-neoplastic cells
-deposition of fibrin / crystals (e.g. calcinosis cutis)

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3
Q

What are the 3 broad categories of infectious differentials?

A

*Bacteria
*Fungal / yeast / algae
*Protozoa / parasites

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4
Q

What are the bacterial differentials?

A

*Furunculosis
*Mycobacteria, Nocardia, Actinmyces
*Bartonella

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5
Q

What are some fungal / yeast / algae differentials?

A

*Cryptococcus, sporothrix
*Blastomyces, Histoplasma
*Dermatophytic pseudomycetoma

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6
Q

What are protozoal / parasitic differentials?

A

*Leishmania
*Neospora / Toxoplasma
*Dirofilaria

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7
Q

What are non infectious differentials?

A
  • Foreign body (plant/Inorganic material →calcinosis)
  • Inflammatory (eosinophilic granuloma)
  • Cutaneous drug eruption, injection reaction
  • Sterile pyogranulomatous dermatitis and panniculitis (Sterile nodular panniculitis)
  • Juvenile cellulitis
  • Histiocytosis
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8
Q

Considering clinical presentation what should be assessed?

A

*Location on body
*Number
*Size
*Ulcerated?
*Pigmentation
*Alopecic?
*Painful / hard / soft / movable / fixed / warm

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9
Q

How would you take a cytology of a nodule?

A

*Fine needle aspirate
*Apposition

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10
Q

How would you take a histology with a nodule?

A

1.Excision of whole nodule
or
2. Punch / wedge biopsy
*Freeze tissue for culture or PCR

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11
Q

What are further diagnostic tests that could be done?

A

*Immunohistochemistry
*Special stains
*PCR
*Biochemistry
*Serology

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12
Q

What are foreign bodies that could form nodules?

A

*Plant material
*Grass awns
*Embedded insect mouth parts
*Suture material
*Porcupine quills

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13
Q

What are endogenous material that could form nodules?

A

*Hair, sebum, keratin
*Calcium salt
*Tyrosine crystals

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14
Q

What is likely to cause infection from a dog bite?

A

Staphylococcus

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15
Q

What is likely to cause infection / nodule with cat bite?

A

*Fusobacterium
*Pasteurella
*Staphylococcus
*Streptococcus

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16
Q

What are the clinical signs of filamentous bacteria causing nodules?

A
  • Nodules and abscesses, with ulcers, draining tracts and cellulitis →anywhere the bacteria are inoculated (mainly extremities, head and neck, and inguinal area) from bite wounds or penetrating foreign bodies
  • Serosanguineous exudate
  • Possible systemic signs – pyrexia, depression. With Nocardia occasional systemic dissemination and pneumonia
17
Q

How is aetiological cause of a nodule diagnosed?

A
  • Cytology +/- special stains (Gram, ZN) – filamentous bacteria might be seen
  • Histology +/- special stains - nodular to diffuse pyogranulomatous dermatitis and panniculitis, with or without tissue grains “sulfur granules”
  • Culture – can take weeks
  • Molecular techniques (PCR, gene sequencing, MALDI-TOF)
18
Q

How are filamentous bacteria nodules treated?

A

*Surgical drainage
*Antimicrobial therapy

19
Q

What are filamentous bacteria that can cause nodules?

A
  • Actinomyces – oral/GI tract, commensal
  • Nocardia - cosmopolitan, soil saprophyte
  • Actinobacillus - commensal organism in oral cavity
20
Q

What are the clinical signs of a saprophytic mycobacteria nodule?

A
  • single or multiple, firm, well‐circumscribed nodules in the skin or subcutis
  • peripheral lymphadenomegaly
  • Canine leproid granuloma (CLG) usually self-limiting
  • Feline leprosy syndromes (FLS) progressive and occasionally aggressive clinical course
21
Q

What can saprophytic mycobacteria nodules form in cats and dogs?

A

*Cats = Feline leprosy syndromes
*Dogs = Canine leproid granuloma

22
Q

How is CLG treated?

A

Spontaneous regression in 1-3 months

23
Q

How is FLS treated?

A

*Combination of 2/3 antibiotics,
*surgical excision

24
Q

What are the clinical signs of a non-tuberculous mycobacteria nodule?

A

*Granulomatous panniculitis - Single/multiple nodules, plaques, macules and diffuse swelling –
multiple punctate ulcers and draining tracts (++ inguinal fat pad, tail base, flank)
* (Pyogranulomatous lobular pneumonia)
* (Disseminated systemic disease)

25
Q

What are the clinical signs of M. tuberculosis nodules?

A

*Firm nodules, ulcerations, non-healing wounds with draining tracts →thick yellow to
green fluid + systemic signs
*+/- local or generalized lymphadenopathy

26
Q

What pets are predisposed to M. tuberculosis?

A

Male outdoor cats

27
Q

What is the treatment of M. tuberculosis?

A

*NOTIFIABLE DISEASE - owner might need TB screening
*Euthanasia / multidrug regimens

28
Q

What cats are predisposed to dermatophytic pseudomycetoma?

A

Persian
DLH

29
Q

How is dermatophyte nodules treated?

A

Systemic antifungals - intraconazole

30
Q

What is the fungal cause of dermatophyte nodules in cats?

A

Microsporum canis

31
Q

What are mycetomas?

A

*pyogranulomatous nodules that contain tissue grains or granules composed of dense colonies of organisms and necrotic debris
* Pigmented fungi
* Unpigmented fungi

32
Q

What is chromomycosis?

A

*subcutaneous and systemic disease associated with pigmented fungal elements
* pigmented hyphal elements but NOT grains in tissues

33
Q

What is Cryptococcosis?

A
  • In the environment (soil, trees, bird droppings)
  • Most common systemic mycosis in cats
34
Q

How are subcutaneous fungal nodules treated?

A

*Azoles - systemic antifungals -itraconzaloe
*Amphotericin B
*Terbinafine

35
Q

What mainly only causes nodular skin lesions in immune compromised patients?

A

Protozoa - toxo, neospora, leishmania

36
Q

What are some immune mediated causes of nodules?

A

*Sterile pyogranulomatous dermatitis + panniculitis
*Eosinophilic granuloma

37
Q

What are histiocytes?

A

overarching term to describe cells of dendritic cell (DC) or macrophage lineage

38
Q

Are histiocytomas a concern?

A

No - solitary lesion that regresses in a few weeks

39
Q

How are histiocytic proliferative disorders treated?

A

*Glucocorticoids
*Ciclosporin

MOD (103 decks)

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